1. Field of the Invention
The present invention relates to a valve timing adjusting device for changing opening and closing timing of one or both of an intake valve and an exhaust valve of an internal combustion engine according to operating conditions of the engine.
2. Description of the Related Art
It has been already known a conventional valve timing adjusting device disclosed in JP 3365199 B in which the device includes a first rotor rotating synchronously with a crank shaft of an internal combustion engine and a second rotor integrally secured on an end face of a camshaft and fitted in the first rotor rotatably relative to the first rotor, wherein a relative rotating position between the first rotor and the second rotor is controlled by advanced side hydraulic pressure or lagged side hydraulic pressure applied by a hydraulic control valve. Moreover, the valve timing adjusting device is arranged so as to lock a relative rotation between the first rotor and the second rotor by engaging a rotation restricting member (lock pin) received in either of the first rotor or the second rotor in an engaging hole formed in the other rotor when stopping or starting an operation of the internal combustion engine where no working fluid is being supplied thereto; and further is arranged so as to release the lock by pressure of the working fluid applied to a lagged side oil pressure chamber.
The conventional valve timing adjusting device is arranged as mentioned above. Accordingly, the lock between the first rotor and the second rotor is released by disengaging the lock pin from an engaging hole by pressure of the working fluid applied to the lagged side oil pressure chamber. At that time, the hydraulic pressure for operating the second rotor in the lagged direction releases an engagement of the lock pin in the engaging hole, however, the lagged side oil pressure chamber communicates with an oil passage of the working fluid supply and exhaust system while the lock pin is engaged in the engaging hole. For this reason, reaction force of the above cam facilitates rotation of the second rotor, but causes the lock pin and the side wall of the engaging hole to gall, which increases the possibility that the lock pin cannot disengage from the engaging hole, thereby bringing the device into out of control.